Difficult question to answer without knowing the current sound characteristics in your system (warm/dark, too detailed and dry, slight brightness, lacking transparency and micro-detail, etc.)

There's lots of information on tube-rolling in the Mini-Torii forum section. In particular, check experiences from Les Lammers.

Personally, I'm currently in the process of fine-tuning mine and so far I've some conclusions, but these do not stem from an exhaustive tube selection, just a particular stash of very useful alternatives. There are many more tubes I could eventually try, but that's not the intent in my case. So, consider these suggestions as mere examples.

The rest will depend on the sound you want to get, as stated earlier (from OA3, OB3, OC3 to OD3 output voltage regulators, for example), and OA2 (VR150) as opposed to OC2 (VR75) in the input voltage regulation, all these possible combinations giving you choices in terms of warmth vs transparency and bass profiles with the output regulation, gain modifications with the input regulation.

This, of course, is always system-dependent and YMMV. You'll need therefore to try some potentially interesting tube alternatives on your own to have an idea where you stand/like and then fine-tune.

I'm not familiar with the 5881, but the earlier mentioned 6V6 choices are very good as well as the stock JJ 6V6 S (although to me, the latter is a little dull in comparison). Reissue Tung-Sol 6V6GT's are just the best I've heard so far (YMMV).

Be patient, as you'll need some time to critically listen the various combinations involved and eventually fine-tune based on your own ears. For example, Brimar 12AT7's (really long burning-in times) are not happy with the Reflektor black glass NOS 6V6's mentioned. For these I recommend the 12AU7 variation 5963, as a better pairing (a smooth driver with nice low-end effect). Brimars have better synergies with the reissue Tung-Sol or the stock JJ 6V6 S's.

Finally, if you are replacing the original tube complement just in grounds of reliability, the only issues I know of are with the JJ EZ-81 rectifiers, and not the rest, which have proven very reliable to me so far.

Thanks for the input guys! Glad to hear the only JJ's with issues are the EZ81's. You make a very good point... one must listen critically before changing the tubes out. Without time for adequate listening and break-in it would be impossible to really *hear* the music coming from the amp.

I agree with Lon. In my experience of 8 months with the M-T and after reading countless reports here and in other forums concerning JJ tubes in general, these are well made.

Many people really mistreat the output types in guitars, for example, and they still prefer them for their ruggedness and sound, with the only caveat that they sound a little compressed compared to a few others.

Having said that, the recent history of early failures with the JJ EZ-81 is so evident, users now tend to replace them prophylactically, before that happens. I'm not sure why Decware continues to ship them with the Mini, but given JJ's good reputation, I guess the expectation is that this is just a bad lot-related, temporary situation.

I would strongly recommend good NOS rectifiers for this particularly critical tube duty.

I personally have experienced premature JJ tube death: a 6V6, 6922's (more than 1) and on the forums there are numerous tales of sketchy JJ quality control and failures. I am sure there are plenty of good JJ's out there, like Lon's E34L's; I even have a few JJ 6922's that are still good. But the failures are mounting and to ignore that seems unwise.

Well, for me three consecutive quads of JJ 6CA7 have performed flawlessly and sonically wonderful as well. And David is right about guitar amps, the E34Ls and 12A series tubes are often used and recommended.